Sertoli cell cultures of rodents will be used to study the transduction of hormone signals as related to cyclic nucleotide metabolism. We propose to: 1. Localize by indirect immunofluorescent techniques the localization of cAMP-dependent protein kinase subunits (R1, R2 and C) and of clamodulin in cultured Sertoli cells. 2. Extend current studies on the cAMP-dependent and Ca2 ion-dependent phosphorylation of proteins of Sertoli cells. 3. Clarify by the combined use of ABP immunocytochemistry and autoradiography the proliferative potential of Sertoli cells in vitro. 4. Biochemical characterization of guanylate and adenylate cyclase and the effects of FSH and pharmacological agents on their localization in cultured Sertoli cells. 5. Sertoli cell-seminiferous epithelium interaction using an interacting co-culture system. 6. Biochemical and autoradiographic studies on the hormone-dependency of RNA synthesis in Sertoli cell cultures. Results of these studies are considered relevant for understanding the cell biology of Sertoli cell coordinated by signals triggered by ligands and chemical messengers.